Sludge tank with self-cleaning screen and screen for use therein

ABSTRACT

A conveyorized sludge tank is provided with a screen mounted at the bottom of the tank for swinging motion toward and away from the flights of the conveyor and adapted to lean against a course of the conveyor to cause the conveyor flights to continuously wipe the filtering surface of the screen. The screen is preferably formed in sections, each of which has spaced filtering strips and the filtering strips of adjacent sections diverge to form a herringbone pattern that minimizes and equalizes wear on the conveyor flights.

United States Patent Hoag [54] SLUDGE TANK WITH SELF-CLEANING SCREEN ANDSCREEN FOR USE THEREIN [72] Inventor: Don ll. Hoag, Erieville, NY.

[73] Assignee: Clarkson Industries, Inc., New York,N.Y.

[22] Filed: Sept. 16, 1970 [21] Appl. No.: 72,746

152] U.S. Cl ..210/237, 210/298, 210/414,

[51 Int. Cl ..B0ld 39/20 [58] Field of Search ..210/154, 155, 159, 162,298, 210/498, 499, 237, 414

[ 51 July 11, 1972 [56] References Cited UNITED STATES PATENTS 1,375,49911/1920 Hunt 210/162 X 2,996,189 8/1961 Salterbach ..2 10/ 155 PrimaryExaminer-John Adee Attorney-Curtis, Morris & Safiord 57 ABSTRACT Aconveyorized sludge tank is provided with a screen mounted at the bottomof the tank for swinging motion toward and away from the flights of theconveyor and adapted to lean against a course of the conveyor to causethe conveyor flights to continuously wipe the filtering surface of thescreen. The screen is preferably formed in sections, each of which hasspaced filtering strips and the filtering strips of adjacent sectionsdiverge to form a herringbone pattern that minimizes and equalizes wearon the conveyor flights.

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I111lllllllllllHHIHIIHHI A "lllli illlillliillli lll |1| 11111 III IIIllllilliu PATENTEDJUL 1 1 I972 SHEET 1 [IF 3 INVENTOR. DON H. HOAGATTORI PATENTEDJUL 1 1 I872 SHEET 3 OF 3 INVENTOR. DON H. HOAG ATTORNEYSFIG. 4

SLUDGE TANK WITH SELF-CLEANING SCREEN AND SCREEN FOR USE THEREIN Thisinvention relates generally to conveyorized sludge tanks of the type inwhich relatively coarse objects are separated by sedimentation from aliquid medium in which 'they are suspended and then removed from thetank by the flights of a moving conveyor positioned partially within thetank. More particularly, the invention relates to a novel filter memberadapted to be used in conjunction with such a sludge tank to promoteclarification of the liquid medium and to a novel arrangement of thefilter member within the tank. The apparatus of the present invention isparticularly well adapted to be used in conjunction with a sludge tankemployed for removing chips of metal from a metal working coolant of thetype used in various machining operations, and will be illustrativelydescribed in connection with such an application. However, as thedescription proceeds it will become apparent that the present inventionis also useful in clarifying other kinds of liquid media having otherkinds of coarse particles or objects suspended therein.

Conveyorized sludge tanks have been commonly used for removal of metalcuttings and other foreign materials from machine tool cutting fluids.Such sludge tanks are primarily settling tanks wherein the suspendedmatter accumulates at the bottom of a tank having a sloping end wall.The transverse vanes or flights of an endless conveyor move the settledsolids along the bottom of the tank toward the sloping end wall, up thesloping end wall and out of the tank to a suitable point of disposal. Ithas been found in the operation of such tanks that when the flow ofdirty" coolant to the sludge tank and removal of clarified coolant fromthe tank is maintained at a practical level, a certain amount of solidmaterial remains suspended in the clarified coolant leaving the tank andthat this suspended matter tends to clog the pump or pumps used torecirculate the coolant to the machining operation.

In an effort to solve this problem, screens have been used at or nearthe clarified coolant outlet from the tank. However, such screens tendto become clogged with solid materials in a relatively short period oftime and require frequent removal for cleaning.

It is accordingly an object of the present invention to provide animproved filter member or screen adapted to be used in a conveyorizedsludge tank to improve the clarification of the liquid component of asuspension being processed therein. It is another object of theinvention to provide in such a conveyorized sludge tank a filter memberso constructed and arranged in respect to the conveyor flights that thefiltering surface of the filter member is continuously wiped or scrapedby the flights of the conveyor to remove accumulated material therefrom.It is a further object of the invention to provide an arrangement of afilter member in a conveyorized sludge tank that reduces the tendency ofthe filter to become clogged. It is still another object of theinvention to provide such an arrangement wherein wear of the filteringsurface and cooperating conveyor flights is minimized and equalized. Itis still another object of the invention to provide such an arrangementwherein the filter member may be readily removed for cleaning. Otherobjects of the invention will be in part obvious and in part pointed outhereafter.

The many objects and advantages of the present invention may be bestunderstood and appreciated by reference to the accompanying drawingswhich illustrate apparatus incorporating a preferred embodiment of theinvention and wherein:

FIG. 1 is a top plan view of a sludge tank showing an endless conveyorand cooperating filter member therein;

FIG. 2 is a side view of the sludge tank further showing the V relationbetween the conveyor and filter member;

FIG. 3 is an enlarged vertical section taken on the line 3-3 of FIG. 1and particularly showing the mounting of the filter element;

FIG. 4 is a front view of the filter member showing the herringbonearrangement of the filter strips thereof; and

FIG. 5 is a detail section taken on the line 5 5 of FIG. 4 showing themanner in which the sections of the filter member are connected.

Referring to the drawings and more particularly to FIGS. 1 and 2, thenumeral 10 generally designates a sludge tank having side walls 12 and14, vertical end wall 16, sloping end wall 18 and bottom 20. Mountedwithin the sludge tank 10 there is an endless conveyor generallydesignated 22 comprising a pair of chain belts 24 and 26 located nearthe side walls of the tank and having secured thereto a series oftransverse flights or scraper members 28. As best shown in FIG. 3 andreferring particularly to the upper portion of FIG. 3, each of theflights 28 comprises an angle iron, one flange 28a of which is securedto a transverse strip 28b which is in turn secured to the chain belts 24and 26, and the other flange 280 of which extends perpendicularlyoutward from the chain belts to provide the desired wiping or scrapingaction.

Reverting to FIGS. 1 and 2, the chain belt 26 is supported on a seriesof sprockets 30, 32, 34, 26 and 38 secured to transverse shafts 40, 42,44, 46 and 48, respectively, mounted for rotation in the side walls 12and 14 of the sludge tank. Chain belt 24 is mounted on similar sprocketssecured to the shafts 40 to 48 near the side wall 12 of the sludge tank.The conveyor is driven counter-clockwise as shown in FIG. 2 throughshaft 48 by a motor 50 through a reduction train 52.

The suspension to be clarified is supplied to the sludge tank 10 throughan inlet connection 54 in the side wall 14 of the tank near the slopingend 18 thereof. Clarified liquid is removed from the tank near the endwall 16 by a pump 56 mounted on a platform 58 attached to the top of theside walls 12 and 14. Extending downwardly from the pump 56 there is asuction pipe 60 having a suction inlet 62 at its lower end.

Within the sludge tank 10 most of the solids contained in the suspensioncharged to the sludge tank settle to the bottom of the tank. As theconveyor 22 is driven by motor 50, flights 28 of the bottom course ofthe conveyor, which are located close to the bottom of tank 20, move thematerial that has settled to the bottom of the tank to the right asshown in FIG. 2 and thence upwardly along the sloping wall 18 to a chuteand thence to a suitable point of disposal.

As has been pointed out above, a certain proportion of the suspendedsolids do not settle to the bottom of the tank during the time that thesuspension is in the tank and in prior sludge tanks this unsettledmaterial has tended to accumulate in the suction of the clarified liquidpump 56 thus clogging the suction of the pump. In accordance with thepresent invention, a screen 66 having a novel construction andarrangement is interposed between the section of the sludge tankcontaining the conveyor 22 and the suction of pump 56.

The construction of the screen is best shown in FIGS. 3, 4 and 5 of thedrawings. Referring particularly to FIG. 4, the screen there showncomprises two sections 68 and 70. Each section of the screen isessentially a grid comprising the horizontal bars 72 having spacedvertical filtering strips 74 secured thereto. As shown in in FIG. 5, thefiltering strips 74 are T-bars with the cross members 76 of the T-barsforming the filtering surface of the screen. The distances between thefiltering strips 74 may be varied depending upon the nature and size ofthe ships or other objects to be filtered.

Also as shown in FIG. 5, the sections 68 and 70 of the screen areinterconnected by means of angle irons 78 and 80. The flange 82 of angleiron 78 is secured to the cross bars 72 of the screen section 70, andthe flange 84 of angle iron is secured to the cross bars 72 of section68. The flanges 86 and 88 of angle irons 78 and 80 are bolted togetherby the bolts 90 to connect the screens sections 68 and 70 to each other.As indicated in FIG. 3, three pairs of angle irons are used along thelength of the screen and at the top and bottom of the screen transverseangle irons 91 and 92 are secured to the topmost and bottommostcrossbars 72 to provide additional structural strength. As shown inFIGS. 3 and 4, screen 66 is provided at its top with the handles and 102to facilitate its removal from the tank for cleaning.

Referring particularly to FIG. 4, it will be noted that the lower endsof filtering strips 74 of section 68 of screen 66 are positionedslightly to the left of the tops of said strips so that the filteringstrips form a small angle with respect to the longitudinal axis of thescreen. This lateral displacement of the filtering strips is preferablymade approximately equal to the distance between the centers of adjacentstrips. In a similar manner the lower ends of filtering strips 74 ofscreen section 70 are laterally positioned slightly to the right of thetops of said strips. Thus the filtering strips 74 of the two screensections 68 and 70 form a herringbone pattern. As explained more fullybelow, this angular arrangement of the filtering strips serves tominimize and equalize wear on the flights 28 of conveyor 22.

The mounting of the screen within the sludge tank and its cooperativerelation with conveyor 22 are best shown in FIG. 3 of the drawings.Referring to FIG. 3, the sprockets 32 are positioned somewhat nearer theend wall 16 of the sludge tank than the sprockets 34 to cause theportion of the conveyor between these sprockets to move along anapproximately vertical but slightly tilted path, hereafter referred tofor convenience as the vertical course of the conveyor. To ensure thatthe conveyor will follow a linear path during its vertical course aguide member 93, secured to the side walls of the tank, is locatedinside the conveyor and adjacent thereto in such manner that theconveyor belt chains 24 and 26 slide thereover. To provide a mountingfor the screen, there are secured to the bottom 20 of tank 10 atriangular abutment 94 and spaced angle iron abutment 96. The bottom ofthe screen and more particularly one flange of the angle iron 92 and thelower ends of the filtering members 74 extend into the space betweenabutments 94 and 96 in such manner that the bottom of screen 66 isremovably and pivotally supported near the bottom of tank 20, but is notconnected thereto. As shown in FIG. 3, the screen is arranged at such anangle that it leans against the flights 28 of the conveyor 22 and issubstantially arallel with the vertical course of the conveyor. Theangle that the screen forms with the vertical will vary with suchfactors as conveyor speed, size and type of chips being filtered and thetype and capacity of the clarified liquid pump. Usually this angle willbe in the range to 30 for good performance.

As the flights 28 of conveyor 22 move downwardly in contact with thefilter members 74 of the screen, they remove any accumulated solids onthe filtering surface of the screen and deposit them on the bottom ofthe tank, whence they are scraped along the bottom of the tank asdescribed above. Since the screen 66 merely rests against the conveyorflights and is pivotable at its lower end, it is free to move away fromthe conveyor flights in the event that any objects are caught betweenthe filtering members 74 of the screen and the conveyor flights and aredifficult to dislodge.

As has been pointed out above, the filtering members 74 of the screensections 68 and 70 are arranged at a small angle with respect to longdimensions of the sections. If the filtering members were preciselyparallel to the longitudinal axis of the screen sections, they wouldtend to wear grooves in the portions of the conveyor flights that wipethe filtering surface of the screen. By positioning the filtering stripsat an angle, wear on the conveyor flights is equalized. Moreover, if allof the filtering strips were displaced angularly in the same direction,movement of the conveyor flights along the filtering surface woulddevelop a torque or other distorting force. By using the herringbonepattern described above, these forces are balanced and a more stableoperation is achieved.

From the foregoing description it should be apparent that the presentinvention provides a filter element and arrangement thereof in a sludgetank capable of achieving the objects set forth at the beginning of thepresent specification. By arranging the screen parallel to the tiltedvertical course of the conveyor, continuous wiping and cleaning of thefiltering surface of the screen is achieved. Since the screen leansagainst the conveyor flights and is held thereagainst by the force ofgravity, and since it is pivotally mounted at the bottom, it can readilymove away from the conveyor if a large ob ect IS caught in the spacebetween the filtering strips, thereby avoiding damage to the filteringsurface. Since the screen rests freely on spaced abutments at the bottomof the tank, it can be readily removed for cleaning.

It is of course to be understood that the foregoing description isintended to be illustrative only and that numerous changes can be madein the specific embodiment disclosed and described without departingfrom the spirit of the invention as defined in the appended claims.

I claim:

1. In filtering apparatus for separating relatively coarse objects froma liquid in which they are suspended, said apparatus being of the typethat comprises a tank for containing the liquid suspension to befiltered, an endless conveyor at least partially immersed in saidsuspension and carrying a series of transverse wiper elements, anupstanding elongated filter member positioned in said tank with itsfiltering surface confronting said conveyor and being in contact withwiper elements of said conveyor, and means for driving said conveyor tocause the wiping elements thereof to move along the filtering surface ofsaid filtering element to wipe said filtering surface, the improvementwhich comprises forming said filter member of a grid of elongated,straight, substantially parallel filtering strips secured to transversesupporting bars, said filtering strips being closely spaced to preventsaid objects from passing therethrough and being arranged at a smallangle with respect to the longitudinal dimension of said grid to preventsaid filtering strips from wearing grooves in said wiper elements.

2. A filter member according to claim 1 wherein said small angle is of amagnitude such that the opposite ends of said filtering strips arelaterally displaced by an amount approximately equal to the distancebetween the centers of said filtering strips.

3. A filter member according to claim 1 wherein said filtering stripsare the crossmembers of T-bars secured to said transverse bars.

4. A filter member according to claim 1 wherein said grid is provided atone end with lifting lugs to facilitate removal of said filter memberfrom a filter tank in which it is positioned.

5. In filtering apparatus for separating relatively coarse objects froma liquid in which they are suspended, said apparatus being of the typethat comprises a tank for containing the liquid suspension to befiltered, an endless conveyor at least partially immersed in saidsuspension and carrying a series of transverse wiper elements, anupstanding elongated filter member positioned in said tank with itsfiltering surface confronting said conveyor and being in contact withwiper elements of said conveyor, and means for driving said conveyor tocause the wiping elements thereof to move along the filtering surface ofsaid filtering element to wipe said filtering surface, the improvementwhich comprises forming said filter member of two or more interconnectedsections, each of which comprises a grid of elongated, straight,substantially parallel filtering strips secured to transverse supportingbars, said filtering strips being closely spaced to prevent said objectsfrom passing therethrough, the parallel filtering strips of adjacentsections diverging slightly from one end of said grid to the other toform a herringbone pattern to prevent said filter strips from wearinggrooves in said wiper elements.

1. In filtering apparatus for separating relatively coarse objects froma liquid in which they are suspended, said apparatus being of the typethat comprises a tank for containing the liquid suspension to befiltered, an endless conveyor at least partially immersed in saidsuspension and carrying a series of transverse wiper elements, anupstanding elongated filter member positioned in said tank with itsfiltering surface confronting said conveyor and being in contact withwiper elements of said conveyor, and means for driving said conveyor tocause the wiping elements thereof to move along the filtering surface ofsaid filtering element to wipe said filtering surface, the improvementwhich comprises forming said filter member of a grid of elongated,straight, substantially parallel filtering strips secured to transversesupporting bars, said filtering strips being closely spaced to preventsaid objects from passing therethrough and being arranged at a smallangle with respect to the longitudinal dimension of said grid to preventsaid filtering strips from wearing grooves in said wiper elements.
 2. Afilter member according to claim 1 wherein said small angle is of amagnitude such that the opposite ends of said filtering strips arelaterally displaced by an amount approximately equal to the distancebetween the centers of said filtering strips.
 3. A filter memberaccording to claim 1 wherein said filtering strips are the cross-membersof T-bars seCured to said transverse bars.
 4. A filter member accordingto claim 1 wherein said grid is provided at one end with lifting lugs tofacilitate removal of said filter member from a filter tank in which itis positioned.
 5. In filtering apparatus for separating relativelycoarse objects from a liquid in which they are suspended, said apparatusbeing of the type that comprises a tank for containing the liquidsuspension to be filtered, an endless conveyor at least partiallyimmersed in said suspension and carrying a series of transverse wiperelements, an upstanding elongated filter member positioned in said tankwith its filtering surface confronting said conveyor and being incontact with wiper elements of said conveyor, and means for driving saidconveyor to cause the wiping elements thereof to move along thefiltering surface of said filtering element to wipe said filteringsurface, the improvement which comprises forming said filter member oftwo or more interconnected sections, each of which comprises a grid ofelongated, straight, substantially parallel filtering strips secured totransverse supporting bars, said filtering strips being closely spacedto prevent said objects from passing therethrough, the parallelfiltering strips of adjacent sections diverging slightly from one end ofsaid grid to the other to form a herringbone pattern to prevent saidfilter strips from wearing grooves in said wiper elements.